The invention discloses a low-voltage load shedding control method for a power system, and the method comprises the steps: responding to a locking condition of the power system, and locking the low-voltage load shedding of the power system; monitoring the voltage of the power system and calculating the change rate of the voltage; starting a low-voltage load shedding unlocking operation according to the voltage of the power system, wherein the low-voltage load shedding unlocking operation comprises the steps that when the voltage is in a continuous low-voltage state, unlocking the low-voltage load shedding after preset fixed delay; when the voltage is in a slow recovery state, unlocking the low-voltage load shedding after a preset acceleration extension link; when the voltage is in the recovered state, unlocking the low-voltage load shedding. The invention further discloses a low-voltage load shedding control device for the power system. By adopting the embodiment of the invention, thelow-voltage load shedding function can be unlocked in time when the low-voltage load shedding lock is caused by large disturbance of the power system.